1. Field of the Invention
The present invention relates, for example, to an electron emission device. More particularly, it relates, for example, to an electron emission device with an enhanced arrangement of electron emission regions and driving electrodes.
2. Description of Related Art
Electron emission devices using a cold cathode as an electron emission source include several types: field emitter array (FEA), surface conduction emitter (SCE), and metal-insulator-metal (MIM).
The FEA-type electron emission devices work because when material with a low work function or a high aspect ratio is used to form electron emission regions, electrons are easily emitted from the electron emission regions under the vacuum atmosphere due to the electric field. The electron emission regions may be formed with a sharp front tip structure mainly based on, for example, molybdenum Mo or silicon Si, or with a carbonaceous material, such as carbon nanotube, graphite, or diamond-like carbon.
The common FEA-type electron emission display has a structure in which first and second substrates form a vacuum vessel, and cathode and gate electrodes are formed on the first substrate, insulated from each other. Electron emission regions are formed on the first substrate and are coupled to the cathode electrodes. Phosphor layers and an anode electrode are formed on the second substrate. The anode electrode makes the electrons emitted from the electron emission regions accelerate toward the phosphor layers.
Cathode electrodes, an insulating layer, and gate electrodes are sequentially formed on the first substrate. Openings are formed at the gate electrodes and the insulating layer. The cathode electrodes are exposed to the outside. Electron emission regions are formed on the exposed portions of the cathode electrodes.
However, with the above-structured electron emission device, when the carbonaceous material paste is injected into the openings and fired to form electron emission regions, the conductive carbonaceous material straddles the cathode and the gate electrodes. This can cause the two electrodes to short-circuit. In order to prevent short-circuiting, it is possible to use a sacrificial layer. However, the processing steps for using the sacrificial layer approach are complicated, and the etchant for removing the sacrificial layer tends to damage other structural components.
U.S. Pat. No. 6,420,726 discloses a structure in which gate electrodes are arranged between the substrate with electron emission regions and cathode electrodes. As the electron emission regions are positioned at the topmost area of the substrate, they can be easily formed using a screen printing technique.
However, with the above structure, the shape and the arrangement of the electron emission regions as well as the interconnection structure of the cathode electrodes and the electron emission regions greatly influence electron emission. Accordingly, when such structural components are not made in a suitable manner, electrons emitted from the electron emission regions can incorrectly stimulate light emission in the phosphor layers of an incorrect pixel (usually a neighboring pixel). In this case, electron emission efficiency deteriorates, and it becomes difficult to obtain the desired screen brightness.